This invention relates to keyboards such as for word processing terminals, and in particular to a means to vary the pressure required to depress the keys.
Keyboard operators are increasingly becoming susceptible to tenosynovitis and repetitive strain injuries. This condition is a result of a situation where the muscles of the forearm become over-worked at the same pressure for long intervals, causing muscle fatigue, mylin sheath irritation and blood stasis. Operators of all types of keyboards even telephone switchboards, are exposed to such a situation.
Apart from the overuse aspect there is also the stress problem caused by the continual impact to the fingers at the end of each keystroke as the key finds its stop position.
Lost time is experienced as operators need to have regular rest periods during typing, to relieve the muscle fatigue.